The Socfin palm oil nursery near Sahn Malen. A report has criticised land deals in Sierra Leone for not benefiting locals. Photograph: Christian Aid

Thousands of smallholder farmers in Sierra Leone have become poorer, eat fewer meals and have taken their children out of school as a result of large-scale farmland investments, according to Christian Aid.

In a report, Who is Benefitting (pdf), which examined the impact of large land leases held by three investors, the NGO found there was an increase in social problems including teenage pregnancy, broken marriages and heightened tension within communities.

"The consensus was that people were worse off than before," Joan Baxter, senior fellow with the Oakland Institute, a US-based thinktank, and author of the report, said. "Companies are making grandiose promises about jobs and development but they will not employ all of the people who were employed in subsistence farming."

The report looked at operations by Addax Bioenergy, a Swiss company and subsidiary of Addax & Oryx Group (lease of 44,000 hectares, or 109,000 acres); Sierra Leone Agriculture, part of SLA Luxembourg, which was acquired by Geoff Palm in 2011 (41,582 ha); and Socfin Agricultural Company (6,500 ha).

Socfin's country co-ordinator, Gerben Haringsma, expressed his exasperation at the report and described it as one-sided.

Sierra Leone is making a major push to attract large-scale agribusiness investments, 10 years after civil war. Since 2009, it is estimated that more than a fifth of the country's arable land (1.1m ha) has been leased to mostly foreign companies for industrial-scale agriculture. The largest land acquisitions are intended for palm oil and sugar cane (for ethanol production).

The government says investments will help boost exports and employment opportunities. But the drive towards large-scale agriculture, backed by the World Bank, and particularly its private sector arm, the International Finance Corporation, has been criticised by groups such as Christian Aid, which warn that social tension arising from large land deals could lead to a return of violence.

The report says: "There was a consensus that they [survey respondents] had agreed to the deals because of promises of many benefits and development, and only a few community members – large landowners – that received surface rents, and those with jobs had seen any real benefits."

Kato Lambrechts, senior policy officer for Africa at Christian Aid, said a key problem was the government's claim that only 11-15% of the country's arable land was being "used", and there was plenty of room for foreign investors.

"This shows a lack of understanding of the way the country's smallholder farmers, who account for nearly half of working age Sierra Leoneans, use the land," she said. "They rely on an extremely diverse and complex mosaic of land types – upland farms, land depressions prone to flooding, swamps, tree-crop plantations, fallow bush and river-line grass areas to grow a wide variety of crops. Much of this land is deemed 'unused' – but that is far from the case."

The report criticises the tax breaks offered to foreign companies to encourage them to invest. It calculates that over a 10-year period an estimated $188.8m in tax revenue will be lost by the government as a result of special tax deals with Addax Bioenergy and Socfin.

The report says that before the investments, people tended to eat two or three meals a day after harvest. This might drop to two, or only one meal a day, during the hungry season. After the investments, people began to eat up to two meals a day, even at harvest, formerly considered a time of abundant food.

Some said they had lost year-round access to fruit from trees on their land, which had complemented their diets, before the trees were felled for the plantations.

In all three lease areas, people said they would not have agreed to the land deals were it not for promises made to them about jobs and the building of roads, along with improved health and education facilities, electricity and water wells.

These had not been fulfilled to their expectations, although the companies maintained that they needed to start full production and receive returns on their investment before they could create all the jobs that had been promised.

Baxter, however, said the situation would not improve unless Sierra Leone implements the report's recommendations, including a binding regulatory framework (based on international guidelines for responsible agricultural investment) for foreign investment in farmland that emphasises protection of local people and the environment, limiting leases to 1,000-2,000 ha, and binding compensation for all crops, trees and important resources based on the real value of each over its productive life span. Until such recommendations are applied, the report calls for an immediate moratorium on large-scale investment in farmland in Sierra Leone.

Haringsma said: "It [the report] is so one-sided it makes me want to cry. I'm so sick and tired of defending myself as if I'm doing something wrong. What we do is not ideal, everything we do could be done better, but today we pay salaries to almost 3,000 people, who have no land and had no job until we came.

"How would the situation be if we are not there? I know the difference we make – wells, latrines, schools, scholarships, zinc on the roofs everywhere, small businesses thriving. Nobody goes to bed hungry in the evening any more."

Haringsma accused NGOs of making it difficult for firms to invest: "As major investors, we do not need Sierra Leone, but Sierra Leone needs us to come out of the miserable situation after the war. To block big-scale rice production projects is in my eyes almost criminal."